Laser Drive Needs Total laser current BIAS Current ITOT = IBIAS + IMOD BIAS Current Keeps ITOT > ITH (laser “on”) IBIAS – ITH related to speed Modulation (MOD) Current Shaped by the data Larger IMOD gives larger signal IBIAS IMOD ITOT

MAX3287 Evaluation Kit

Test Setup for Maxim board Tested to verify its functionality Two test conducted for Maxim board DC coupled output of Maxim board AC coupled output of Maxim board Equipment used 5V power supply SMA cables and connectors Oscilloscope and function generator

Test Results for Maxim board DC coupled Near perfect open eye Fits the compliance mask Signifies very low SNR Slight dip at the bottom (unexplained phenomenon)

Test Results for Maxim board AC coupled Again a near perfect open eye Low SNR Fits the compliance mask The dip on bottom disappears (mysteriously)

Circuit from unstuffed part of MAX 3287 Eval board Remove feedback loop PD, bias adjustment PNP

Circuit from unstuffed part of MAX 3287 Eval board Keep almost all other components Use Eval board part numbers for inductors (ferrite beads)

Design elements Match load on OUT- with OUT+ as well as you can Need to adjust Laser DC Bias current Need to adjust Laser modulation current